199. Studies in the synthesis of terpenes. Part VIII. The absolute configuration of elemol

Abstract

The absolute configuration of elemol has been proved to be as shown in formula (V) by a synthesis of eleman-2,3,1 l-trio1 (XXXIII) from (+)-epia-cyperone (XI), a sesquiterpene of known absolute configuration.ELEMOL is a crystalline, unsaturated, tertiary-alcoholic sesquiterpene which has structure An indication of its relative stereochemistry is given by the formation of the lactone (111) from dihydroelemol (11), while the isolation of eudesmane (IV) on hydrogenation of the mixed hydrocarbons obtained by pyrolysis of elemyl benzoate or p-nitrobenzoate suggests, but does not prove, that the absolute configuration is as in structure (V). This has now No decisive proof of its absolute configuration has been published. * Part VII, J . , 1961, 4211.

The chemistry of thujone. VII. Thujone as a chiral synthon for the preparation of sesquiterpenes. Synthesis of β-elemol

“…The latter compound has been previously reported (9) as a glass ([a],-10") and obtained from elemol.…”

Stereoselective Total Synthesis of Copa and Ylango Sesquiterpenoids: Preparation of (−)-(1S,4S,5R,7R)-1,7-Dimethyl-4-isopropylbicyclo[3.2.1]octa-6,8-dione and(+)-(1R,4S,5S,7S)-1,7-Dimethyl-4-isopropylbicyclo[3.2.1]octa-6,8-dione

“…It is well known that Robinson annelation of (+)-dihydrocarvone (36)" with l-diethylamino-3-pentanone methiodide affords a mixture of products, of which the crystalline, easily isolable ketol37 predominates (an average of -65% isolated yield in our experiments) (31,32). For our synthetic purposes, the established trans configurational relationship between the isopropenyl group and the angular methyl group was of crucial importance.…”

Hedycaryol – Central Intermediates in Sesquiterpene Biosynthesis, Part II

“…Subsequently, the same workers also described 2 as the product of a thermal Cope rearrangement of hedycaryol ( 1 ) [23] . The absolute configuration of 2 has been established independently by chemical correlations to tetrahydrosaussurea lactone [24] and (+)‐10‐ epi ‐α‐cyperone ( 5 ) in a procedure involving epimerisation of the side chain attached to C7 (Scheme 2B) [25] . Reduction of 5 with Li in ammonia gave trans ‐fused 6 that was converted with isopropenyl acetate and p ‐TsOH into enol ester 7 , followed by ozonolysis and esterification to 8 .…”